How to refer to an image by it's label name (Python)
If that is going to be the only texture coordinate node in the tree something like this might be adequate:

import bpy

mat = bpy.data.materials[0]

tcs = [ node for node in mat.node_tree.nodes if node.bl_idname=="ShaderNodeTexCoord"]
# python list comprehension filters the list of nodes down to the ones that match the right bl_idname

tcnode = tcs[0]
# grab the first node of the one(s) that match the bl_idname